pretty much keep in mind that the conclusion must address the aim of the experiment. so if the aim is To Observe the effects of "this" on "that", the conclusion would be "This" did this to "that". Make sure not to just restate or list ur reuslts in ur conclusion... our teacher always marked us wrong when we did that.
the discussion would be more a past tense recount of what happened, This happened and this is why, for example.